Price: FreePros: Great way to map small WLANs, relatively accurate, can't beat the price (free!)Cons: 15 minute survey limit, no pan/zoom, no result save (beyond snapshots), XP/Vista only

Large WLANs are best designed and mapped using sophisticated planning and site survey tools. But most home and small business WLANs are "plug and pray"install one AP (or maybe a few) and hope that does the trick. When it doesn't, somebody wanders the area, scanning for nearby APs with an ordinary Wi-Fi client or shareware "stumbler."

While such tools can record vital WLAN stats (e.g., SSIDs, MAC, RSSI), they don't make it easy to pinpoint AP locations or visualize their coverage. Real-time locationing vendor Ekahau has now filled this gap with HeatMapper, a simple, clean, and surprisingly effective bit of Windows freeware.

Keep it simple

Ekahau recommends that WLANs with over five APs invest in sophisticated Site Survey products for multi-floor/building 3D mapping, expert RF planning, load simulation, design optimization, and real-time tracking. While HeatMapper leverages the same positioning engine, it is not a stripped-down version of Ekahau Site Survey Standard or Pro. Rather, HeatMapper is a basic utility, designed specifically to map small WLANs with minimal user input or interpretation.

Home owners and small office staff with no Wi-Fi knowledge can easily use HeatMapper for brief, informal site surveys. Just run the installer on any Windows Vista or XP (32-bit) laptop with at least 512MB RAM, 1GB HDD, 500MHz CPU, and any Wi-Fi adapter. The program auto-launches a 2D map, plotted on a basic grid or any imported image (e.g., a drawn-to-scale JPG of your home's floorplan). Move slowly throughout a single floor, left-clicking at regular intervals to mark your current location (aka "drop breadcrumbs"). You can pause, undo, or add to the current survey at any time, taking measurements for up to 15 minutes.

HeatMapper correlates those clicks with Wi-Fi observations, crunching data to position each discovered AP on the map. Each vendor-specific icon is surrounded by colored bands that represent signal strength range. By default, HeatMapper displays the aggregate coverage afforded by all APs, but hovering over a single AP displays coverage for that device only. This simple and intuitive heat map makes its easy to spot areas with strong (green) or weak (red) coverage. Hovering over any band displays the range (e.g., dark green = received signal strength of -35dBm or greater).

HeatMapper also displays a sortable list of APs, described by SSID, MAC, channel, type (a/b/g/n), max data rate, encryption (open/WEP/WPA/WPA2), and a real-time signal strength meter. These can be used to spot co-channel interference or basic configuration mistakes. For example, you might notice that your AP reverted to open during last night's power failure, that someone installed an AP in the lobby without permission, or that a neighbor is using a channel too similar to yours.

These are very common problems that are easy to fix once you notice them. Other basic Wi-Fi utilities can detect these issues, but HeatMapper gives you more information to resolve them. For example:

NetStumbler might discover neighbors using channels 1, 6, and 11but HeatMapper lets you visualize those AP footprints so you can choose the best alternative.

Your own AP might make you aware of nearby roguesbut HeatMapper helps you pinpoint each rogue's location.

Any Wi-Fi client's signal strength meter might clue you in to troublebut HeatMapper plots the area(s) that could use improvement and the actual consequences after repositioning an AP.

Click to enlarge.

Just the basics

As free utilities go, HeatMapper is a gem. It doesn't require specific Wi-Fi adapters or custom drivers. It isn't beggar-ware or cripple-warethere are no registration nags or buttons that require payment to unlock. It doesn't exit unexpectedly or freeze your laptop. HeatMapper does what it does cleanly, with professional-looking results.

During our tests, HeatMapper accurately estimated the location of interior APs in several small indoor venues, including homes, coffee shops, hotel lobbies, and small offices. Although it was not good at larger, outdoor surveys (like slowly war-driving an entire block), HeatMapper did indicate the general direction of external APs by placing them at the map's outer edge.

HeatMapper may be easy to use, but it's still essential to click correctly and often. In particular, don't just walk the edges of a building or coverage areaaccuracy is far better if you walk in between APs in at least four directions. Repeating an earlier walkabout in the same session can also be helpful; additional readings refine your earlier results.

However, HeatMapper is only designed to map small venues. To survey an area larger than a typical home, you'll need to subdivide and map separately. Why? You can run HeatMapper as often or as long as you want, but it only uses the last 15 minutes of data. If an active survey runs longer, earlier breadcrumbs disappear. Furthermore, the map that HeatMapper produces cannot be scrolled or zoomed; this makes it difficult to survey a large area with sufficient accuracy.

In addition, the more APs, the more cluttered your map becomes. Virtual APs (APs that beacon multiple SSIDs) appear as discrete icons, layered on top of each other. You cannot simultaneously view coverage areas for multiple selected APs (to visualize overlap) or filter out neighbor AP coverage areas (to focus on two or more of your own APs). In short, if you have a large WLAN (or a densely-deployed small WLAN), HeatMapper is not designed for you.

Moving up the food chain

Ekahau has done a nice job of meeting simple SOHO needs with a free utility that does not cannibalize its commercial product sales. But we think there's room in the market for an entry-level 2D mapper that does more without a price tag above two grand.

For example, HeatMapper can sort discovered APs by signal strength, channel, SSID, MAC, or security. However, many small businesses could benefit from grouping APs differently or filtering data used to generate the map. You might want to see your entire "guest" SSID footprint, even if produced by five APs. Or you might want to see a physical AP's composite footprint for all SSIDs it beacons. Perhaps you'd like to see only 5 GHz coverage, or only a single channel.

These are no doubt easy refinements to HeatMapperbut they would start to clutter an otherwise simple utility aimed at novices. On the other hand, SMBs that just can't afford Ekahau's Survey products would probably pay for these value-adds.

The verdict

Of course, Ekahau might do a few things to make this freeware even better. We would love to see HeatMapper on other platforms with touch-screens. Signal strength is useful, but quality is what counts; we'd like to see RSSI and SNR. We also found launching another survey by accident a bit too easy; an explicit Start/Stop button could avoid this.

Finally, HeatMapper can save the currently-displayed map image, but not the list of APs. (To capture both, take your own screensnap.) SOHOs that use HeatMapper for real-time visualization will still need something like NetStumbler to record and compare past survey results. We'd love to be able to save and re-open past HeatMapper runs.

But frankly, these are nits. HeatMapper brings something to the Wi-Fi utility table that's been missing for a long time. When dining for free on a tasty meal, we should really just say "Thank you!"

Lisa Phifer owns Core Competence, a consulting firm focused on business use of emerging network and security technologies. A 27-year networking industry veteran, Lisa has been involved in the design, implementation, and testing of wireless products and services since 1996.

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